In scan conversion systems having a storage cathode-ray tube of the type employing a single electron gun, hereinafter referred to as storage tube, the electron gun must be used for reading, erasing, and writing. Present scan conversion systems employ the read scan raster for erasing and discontinue reading during erase time. Another method employs destructive readout during the read time causing the scanned area to erase over a period of several milliseconds. In the latter method, the area scanned and viewed on a monitor device is erased in a controlled manner.
In U.S. Pat. No. 3,088,048 means are fully described whereby the persistence of the image is electrically controlled using a separate viewing or reading gun for a direct storage tube i.e., electronic storage system for presenting a series of applied electrical signals as a corresponding series of visual images, each of the visual images persisting until converted into the immediately succeeding visual image.